In fiber optic communication, the optical signal propagates inside an optical fiber. Due to the nature of optical fibers, optical signal attenuation always exists. To overcome this signal attenuation in long distance communication systems, optical signal amplification using an optical amplifier is required. Both Erbium Doped Fiber Amplifier (EDFA) or Raman Amplifier can be utilized as the optical amplifier. In order for the optical signal to propagate a longer distance, an optical amplifier with high output power is preferred. FIG. 1 depicts a conventional optical amplifier system 10 for use in high power optical amplification applications. The conventional optical amplifier system 10 includes a wavelength division multiplexer (“WDM”) 14, a first isolator 18, a polarization beam combiner (“PBC”) 22, a second isolator 34 and a tap 38. Also depicted are pump laser sources 28 and 30, which provide a pump signal typically somewhere in the 1400 nm to 1500 nm range, and that are used to amplify the input signal 12 that is input.
The conventional optical amplifier system 10 takes the outputs from the pump lasers 28 and 30 via fibers 24 and 26, respectively and combines the outputs via the PBC 22 so that higher pump power is obtained. The combined pump output 20 is provided to the first isolator 18, which prevents back reflections from reaching the lasers 28 and 30. The isolated pump output 16 of the first isolator 18 is combined with the signal 12 using the WDM 14. Thus, the signal is amplified. The output 32 of the WDM 14 is provided to the second isolator 34, which also precludes signal back reflection. The output 36 of the second isolator 34 is provided to the signal tap 38. The signal tap 38 provides an output signal 40 as well as a tap 42 to be taken from the output signal 40. The tap 42 allows the signal output 40 to be monitored.
Although the conventional optical amplifier system 10 functions, one of ordinary skill in the art will readily recognize that there are a large number (five) discrete components used: the WDM 14, the first isolator 18, the PBC 22, the second isolator 34 and the signal tap 38. Because of the large number of components used, more fusion splicing is required to fabricate the conventional optical amplifier system 10. Consequently, the insertion loss for both the amplified signal and the pump power from the pump lasers 28 and 30 is increased. The performance of the amplifier system will thus be degraded. Furthermore, assembly of the conventional optical amplifier system 10 is made more difficult due to the large number of components. Moreover, the cost of the conventional optical amplifier system 10 is substantially increased because of the large number of components used.
Accordingly, what is needed is an optical amplifier system and method which is more integrated and which amplifies an optical signal. The present invention addresses such a need.